The present invention relates generally to modified flavor characteristics of tabacco, and more specifically to a method for modifying the smoking flavor characteristics of cured bright tobacco with ammonia and without the addition of ingredients extraneous to tobacco.
Treatment of tobacco with various forms of ammonia has been a step employed in many tobacco-processing methods. Gaseous ammonia has been classically employed to prevent the growth mold or sweating of tobacco (see, e.g., U.S. Pat. No. 246,975) and more recently as a means to displace and effect release of nicotine. Representative of such denicotinization processes are those disclosed in U.S. Pat. Nos. 1,640,298 (Sartig), 1,719,291 (Federmann), 2,136,485 (Berka et al.), 2,162,638 (McCoy), 2,227,863 (Rhodes), and 3,742,962 (Brochot). In some of these processes the ammonia gas is combined with another agent, e.g., steam, acetic acid, carbamic acid, hydrogen peroxide or an alkali hydroxide. In every instance, there is removal of components, notably nicotine, from the tobacco and generally speaking no effort is made to maintain the presence of ammonia without dilution or removal.
Aqueous ammonia solutions have been employed in procedures for extracting nicotine from tobacco and in procedures for expanding tobacco. Rhodes U.S. Pat. No. 2,227,863 extracts tobacco with fluorocarbons after pretreatment with a dilute aqueous ammonia solution; Fienstein et al. U.S. Pat. No. 2,525,785 employs ethylene dichoride and aqueous ammonia for the same purpose. Ammonia was disclosed as an expansion agent for tobacco by Armstrong et al. U.S. Pat. No. 3,771,533. This process involves impregnation of tobacco with liquid or gaseous ammonia and exposure of the resulting tobacco to very rapid heating in unconfined (open vessel) conditions to bring about expansion with release of the ammonia. Similarly, Merritt U.S. Pat. No. 4,266,562 employed liquid ammonia and carbon dioxide for expansion.
Improvements in non-tobacco smoking materials have also been achieved by the extractive removal of selected components using liquid ammonia. For example, in U.S. Pat. No. 4,079,742, a non-tobacco smoking product is made by pyrolyzing a cellulosic material and then extracting pyrolytically generated tars with basic liquids, such as liquid ammonia, to effect a 15% to 40% reduction in the weight of the pyrolyzed cellulose.
Finally, ammonia has also been employed in the area of flavoring tobacco. Rainer U.S. Pat. Nos. 4,123,592 and 4,184,495 incorporate volatile flavorants into smoking material through impregnation in liquid ammonia solvent or ammonia mixed with a co-solvent. The liquid ammonia, acting as a swelling agent for the cellulosic polymer structure, allows migration and incorporation of the flavor molecules into the polymers.
The foregoing treatments of the prior art employing ammonia are directed to a variety of results, e.g. expansion, extraction and flavoring, and are generally of a complex, multi-step nature causing significant chemical and/or physical transformation, sacrificing considerable weight fractions of the tobacco undergoing treatment, and frequently resulting in the accumulation of by-products representing a disposal problem.
There remains therefore a need in the art for a simple treatment process for employing ammonia to improve the smoking quality of tobacco material, involving minimal losses of product weight and without the addition of extrinsic matter to the tobacco, which upon pyrolysis may be undesirable.